Bobbin for sewing machines



May 10, 1938. 7 E RUB-EL 2,116,982

BOBBIN FOR SEWING MACHINES Filed Jan. 4, 1935 v INVENTOR: I Charles W W rromvgys.

Patented May 10, 1938 I a y Charles F. Rube], Chicago, Ill., assignor to Union ,Special Machine Company, Chicago, lli., a corporation of Illinois Application January 4, 1935, Serial No. 419

p p p Claims. (01. 112-251) This invention relates tdbobbins' for sewing that the force required to pull oil the thread demachines, and more particularly tobobbins of creases as the diameter oi the threadmass dithe type associated with rotary hooks or loop minishes. Furthermoreislichl bobbins are} not taking mechanism of a likecharacter. re-flllable, and they are objectionable on account 5 The invention deals with the problem of preof the tendency ofthe threadto slip between the 5 venting breaking of the bobbin thread under ends of the mass of wound; thread and the nonconditions where a very fine thread is used, or rigid disks and tobe caught there. Where the threadis subjected to an unusually The principal object of the p ent invention severe-strain on account oi themachines' being is o D l 6, b which $0 des ed a d operated at a high speed and with a relatively P P 'P n Weight w th respectto the 10 long length f 3 threadmass'adaptedto be carried thereon, that r Heretofor it has e customary with rbtary it offers a substantially constant resistance to hook sewing machines to use a steel bobbin hav-' j fl w i t s threadas it i s at ing a weight several times greater than that of its or 1 velocity, thus avoids t contained thread mass, and when'such machines abWQmentwned dimculties which h v been are operated at a high speed, especially where i j Perienced with ld r I bob fine threads and long stitches are used the bobd t s h i the Di s bin thread is apt to break before the entire invent1on, includingthose der ved from the use supply of thread on the bobbin has been used Wbobbm which mem S t oftmmjrm 2 up. With this type of sewingniachine, the boband whim is Sumciently rigifl W binthread is drawn out only during that part mit l more. apparent the cycle which the feed mechanism opp from thedescription hereinafterset forth of one erates, though the pull caused by the movement example of the e f h v n oi the fabric may be supplemented by other facrefemnce to fi mp nfl r tors including the action of the takeup mechof the drawing- 25 anism in drawing theloop of bobbin thread up g- 1 represents fragmentary view h w s to the point where the stitchisjset. Inasmuch the stitch forming parts of sewingtmachme as the feed mechanism operates in timed relaembodying thiiinvenfionh wink Plate Of-the tion to the strokeof the needle, ii" the machine machine being shown nil-cross S n t is operated at a hig speed. the bobbin thread hkiherebenegth b t end will be drawn out with an intermittentpull of @f I i Fig. 11 represents a cross section of the rotary correspondingly high periodicity. Moreover.

a i i r i i hook and parts associated therewith, taken as while the machine operates, the diameter of the indicated by the lines en of Fig.

thread mass carried on the bobbin becomes H m t t h smaller; and the force required to pull of! sucb i' p g zs apersvpggtivgview P h cessive increments of thread of the same length g e t rotary i becomes correspondingly greater, for the bobbin represen s g Ph in he load is rotated through-i morel-degrees of are and the characteristics of: a bobbin of i this invention as pull on the thread is applied closer to the axis compared with steel 5 paper p b i of the bobbin. 1 The gradual reduction in the In the d n the invention Shown as weight of the thread mass is a factor tending to plied lock stitch sawing maFhme th type reduce the forcerequired to pull of! the thread, described m the pendmg apphcation for but where the, bobbin is considerably heavier figg gg ggggg ii gfi igg ghg g h g than itscontained thread mass, which is the case a 1 s a M s 45 with the ordinarysteel bobbin, this factor is not suiiicient to offset the previously mentioned facs a: gfg f ea Whig? tors which tend to increase this force. t h work bein P i epresented 2 i In ie l p thfiordmary steel bobbins it The stitch forming i nechanis m i zffi s a :eedle has been proposed for reasons convenienbe 25 and a rotary hook 26. t The rotary hook 28 '60 a sfa enea A e wor su port type are also characterized by a variable resist- As most clearly shown in Fig. II, the rotary ance to unwinding. Such a bobbin weighs conhook 2G hasan annular raceway "engaged by siderably less than its contained thread mass so, a peripheral rib 29onthe bobbin holder 3|. 55

Within the bobbin holder 3|, the bobbin case 32 is inserted. This case 32 is formed with a sleeve 33 which surrounds a central stud 34 attached to the bobbin holder 3|. The bobbin 3! fits within the bobbin case 32 in surrounding relation to the sleeve 33 and is adapted to rotate freely thereon.

In Fig. I of the drawing, the needle thread is indicated at "and the bobbin thread at 31. The work 24 is engaged from beneath by a feed dog 38 and from above by a presser foot 39. As is well understood by those skilled in the-art, during one part of the cycle of operation the work 24 is moved transversely over the supporting bed 23 by the feed dog 38: and during another part of the cycle of operation the needle 25 passes through the work 24, and a thread loop is taken therefrom by the rotary hook 26 and carried around the bobbin thread 31 to form the stitch.

As most clearly shown in Fig. III, the bobbin desirably consists of 'a tubular core 4| and circular disks 42- secured to the ends of the core. When the bobbin is initially placed in use, the thread is' wound thereon, as indicated at 43 in Fig. II, in such manner as to substantially fill the space defined between the disks 42.

In accordance with the practice of this invention, the bobbin 35 is made of such material and of such physical proportions that the difficulties heretofore experienced with older formsof bobbins are avoided. On the one hand, the material of the bobbin must be suificiently light in proportion to the weight of its contained thread mass that the inertia of the bobbin, 1. e., its resistance to rotation incident to thethread pull, does not materially increase as the thread is drawn off at a uniform linear velocity. Whereas it is characteristic of the" steel bobbins in common use that the resistance offered to rotation increases very considerably as the bobbin unwinds, with the result that when the machine operates at a.

high speed with .a fine thread, the thread will break before the entire bobbin content is consumed, it is characteristic of the bobbin of this invention that the resistance to the thread pull does not increase to any material extent, and

there is therefore no tendency for the thread to break under such conditions. On the other hand, the material of the bobbin must be rigid or nonfiexible, in contra-distinction to paper bobbins, so that the shape of the disks will not become distorted and the bobbin. may be re-fllled and used for a long period of time.

Moreover, the bobbin of this invention is desirably so designed that the resistance offered to its rotation is substantially constant throughout all stages of thread consumption, thus producing an even stitch as well as avoiding any tendency of the thread to break. With the type of bobbin which is customarily employed in rotary hook machines, the outside diameter of the thread mass is substantially twice the inside diameter and I have found that to obtain a condition 'of constant load with a bobbin of this character the weight of the bobbin by itself should be substantially equal to the weight of the thread mass which .it is adapted to contain; One material which may be used to produce a satisfactory bobbin having the desired load characteristics is an aluminum alloy known commercially as lynite", but it is to be understood that the particular composition of the bobbin is relatively unimportant so long as the material is suihciently rigid v the same-conditions.

several bobbins selected forplotting these curves.

so that the bobbin may be re-wound and of such weight, in proportion to its contained thread mass, that the conditions outlined above are obwhen the thread pull is applied tangentially to the core, as it is at the initial stage, when the thread pull is applied tangentially to the circumference of the filled bobbin. From various tests and observations it appears that to produce a constant load bobbin the ratio of the weight of the bobbin by itself to the combined weight of the bobbin and its thread mass should bear the same proportion as the ratio of the initial angular-velocity to the final angular velocity of the bobbin. Thus with bobbins which are so constructed that the initial angular velocity is substantially one half of the final angular velocity the weight of the bobbin by itself should besubstantially one half of the combined weight of the bobbin and the initial thread mass.

The relation of the weight of the bobbin to the weight of the thread mass, and the effect of this relation upon the operation of the machine; is graphically illustrated in Fig. IV. The chart shown in this figure shows the characteristics of ordinary steel and paper bobbins, in com-. parison with the characteristics of a bobbin of this invention. The ordinates of the graphrepresent arbitrarily selected units of force required to' draw out the bobbin thread at a uniform rate of speed. The abscissae represent feet of thread length, or alternatively seconds of time, and reading from left to right show the various stages 'of thread consumption from the point where the bobbin is filled to its capacity with the thread to the point where the thread is entirely consumed. The curve shown at a: represents an example of the action of a steel bobbin, showing the force required to draw oil. the thread during various stages of thread consumption. The curve shown at y represents an example of the action of a paper bobbin under the same conditions; and the curve shown at 2 represents an example of the action of a lynite bobbin under The characteristics of the including the weight of the bobbinby itself, the weight of the original thread mass, the length of the thread, and the weight of the combined bobbin and thread mass, are represented by the following table:

W ht A t W i ht Cmingine? erg moun e g we t 0 Type bbbin of bobbin ofthread of thread bobbin and thread Gram: Yards Grams Gram It will be observed from the above table that the weight of the lynite the curves was approximately equal to the weight of the thread mass contained thereon, whereas the steel bobbin was several times heavier than its thread mass, and the paper bobbin was several times lighter than its thread mass. As shown by the curve a, the force required to draw oiI thread at a uniform rate of linear speed from a steel bobbin of the usual form increases very considerbobbin, used for plotting ably as the thread is consumed, this force beini substantially twice as great at the end of the period of thread removal than at the beginning. As shown by the curve 1.! the force required to draw the thread from a paper bobbin decreases very considerably from the beginning to the end of the period of thread removal, the initial force being more than twice as great as the final force. n the other hand, as shown by the curve represented at e, the force required to pull thread from a lynite bobbin made in accordance with this invention is substantially constant throughout all stages-of thread consumption. a The upturned hook at the right hand end of each curve represents the increase in the final load on the last two or three feet of thread which results from the irregular winding of the first few turns on the bobbin core.

As illustrated by the curves described above, where the bobbin is substantially equal in its weight to the weight of the contained thread mass, its inertia is substantially constant as the thread unwinds, and hence the force required to pull oif successive increments of thread of the same length is substantially constant. This results in a stitch of uniform character and makes possible the operation of a machine at a high speed, using a relatively long length of stitch and a relatively fine thread. Accordingly. the present invention avoids many disadvantages inherent in bobbins which have heretofore been employed in sewing machines.

While this invention has been described with reference to a particular-type of sewing machine,

-' it will be understood that the invention is applicable to other types of sewing machines, and

bination with loop taking mechanism of a sewing machine, said bobbin being so proportioned and of such material that the ratio of its initial angular velocity when the contained thread mass starts unwinding to its final angular velocity when the thread is entirely consumed is substantially equal to the ratio of the weight of the bobbin by itself to the combined weight of the bobbin and its initial thread mass.

2. A thread carrying bobbin for use in combination with loop taking mechanism of a sewing machine, said bobbin being designed to carry an initial thread mass whereof the outside diameter is substantially twice the inside diameter, and said bobbin having a weight substantially equal to that of said initial thread mass.

3. A thread carrying bobbin for use in combinationwith loop taking mechanism of a sewing machine, said bobbin comprising a tubular core and disks thereon defining a space for a mass of thread, the diameter of said thread mass being substantially twice the diameter of said core, and the combined weight of said core and disks being approximately equal to the weight of the con-, tained thread mass filling said space.

4. A thread carrying bobbin for use in combination with loop taking mechanism of a sewing machine comprising a core serving as a bearing and disks thereon defining a space for a mass of thread, said core and disks being of such proportions and of such weight with relation to the weight of the thread mass adapted to fill said space that the inertia of the bobbin with its thread mass remains substantially constant as the thread unwinds at a uniform linear velocity.

5. In combination, a rotary hook for a sewing machine, and a thread carrying bobbin adapted to rotate freely therein, said bobbin being of a material of such stiffness that the bobbin may 

